Tremendous progress has been made, during the past 50 years, in continuously decreasing the size of electronic circuits and increasing the density of electronic components within integrated circuits to produce a plethora of high density, high speed, and low cost integrated circuits used in computers, automobiles, personal digital assistants, cell phones, and thousands of other consumer products, machine tools, scientific instruments, communications devices, and other important products. However, it is currently becoming increasingly difficult to continue to decrease the size of transistors, diodes, signal lines, and other components of integrated circuits produced by photolithography-based methods. Not only must new, expensive fabrication facilities for conducting photolithographic methods using shorter-wave-length radiation be constructed, but basic physical limitations in traditional circuit-manufacturing methods and materials are leading to slower development and slower exploitation of next-generation, denser circuitry.
Recently, an alternative to traditional, photolithography-based integrated-circuit design and fabrication has emerged. It is now possible to create nanoscale, molecular-electronic circuits using nanowires and nanowire junctions with controllable electronic properties to produce nanowire-crossbar circuits that can be configured to implement a large variety of logic components and circuits based on logic components. However, nanoscale circuitry needs to be integrated with sub-microscale and microscale circuitry in order to produce useful devices and products that incorporate nanoscale circuitry. Nanowire crossbars can be fabricated by allowing nanowires to self-assemble into layers of parallel nanowires, circumventing the need to painstakingly and precisely position nanowires within nanoscale circuits. Interfacing nanowires to sub-microscale and microscale circuits remains, however, a challenging problem. Individual nanowires need to be aligned with sub-microscale-components and component patterns in order for signals to be input to, and received from, high density nanoscale circuits. Similar alignment problems are also encountered in purely nanoscale devices, including various types of nanowire crossbars. Designers, manufacturers, and users of integrated circuits and electronic devices have recognized the need for cost-effective and reliable methods for interfacing sub-microscale and microscale electronic circuits to nanoscale circuitry and for producing nanowire crossbars, hybrid microscale/nanoscale crossbars, and other devices that include groups of parallel nanowires.